Insulating oil



Patented Sept. 1932 RICHARD MICHEL, O1 UEBDINGEN, ITIIDEBBHEIN,

GERMANY, ABSIGNOR TO I. G.

FABBENINDUSTBIE AKTIENGESELLS CEAIT, OI IRANKFORT-ON-THE-EAIN, GER- I MANY, A CORPORATION OF GERMANY met-mums on.

No Drawing. Application filed July 12, 1828, Serial No. 292,828, and in Germany July 1-8, 1927.

The invention relates to insulating oils in particular to transformer and switch oils. Insulating oil especially transformer Oll has two principal functions(1) To act as an insulating medium, and (2) to carry the heat generated in the windin and core of the transformer or other circults to the cooling surfaces.

This double function involves that insulating oils have to meet particularly high opcrating conditions. In order to warrant insulating properties answering all require ments of practice, their dielectric strength is not permitted to fall below a minimum and in order to have a good cooling efi'ectythe viscosity dare not exceed a maximum. It is further necessary'to select an oil extremely stable to increased temperature and to oxida- Hitherto mineral oils of suitable properties have been almost exclusively used as insulating oils. According to their geographical origin and according to the special mode of preliminary treatment (refining etc.) they vary within wide limits and tend to undergo detrimental alterations which become evident during the use of such oils.

I have found that alkylated hydrocarbons of the naphthalene series and their derivatives are excellent insulating oils in particular transformer and switch I oils. Especially those hydrocarbons of the naphthalene series have been found suitable which have several side chains and the saturated side chains of which contain two and more carbon atoms. In addition to these alkyl groups one or more methyl groups may also be present in the molecule. Derivatives of alkylated hydrocarbons of the naphthalene series such as hydrogenated naphthalene hydrocarbons or' allrylated naphthalene compounds which are substituted by chlorine in the aromatic nucleus likewise may be used. A considerable number of compounds showing the aforesaid chemical characteristics can be prepared and it is necessary to select among them those liquid com ounds that will have a specific gravity su ciently below 1 and a vapor tension sufiicien'tly low as to answer the requirements prescribed for flash point, constance in weight and other physical characteristics.

distillable under reduced pressure.

The'new insulating oils have a constant chemical composition and their physical e easily adapted to the spepropriate compounds, theoperating conditions of particular cases,

. On the other hand the oilsare desired to be being below 0.1 (German testing method v known "as Verteerungszahl). The oils unite a viscosity within the right limits and a very deep pour point which is frequently below 20 C. They, too, are free from any ingredients insoluble in benzene such' ,as asphalt and other detrimental constituents and are miscible with other appropriate oils e. g. mineral oils. 1

In order to give examples of the new insulating oils I name the oily products which are obtained by reacting with olefines or gases containing olefines in the presence of a catalyst upon naphthalene or homologues of naphthalene e. g. methyl naphthalenes, partially hydrogenated naphthalenes e. g. tetrahydronaphthalene,naphthalenehydroc'arbons being substituted by chlorine in the nucleus e. g. aor fl-chloronaphthalene ar-chloro tetrahydronaphthalene etc.; but I wish to be understood that alkylated naphthalene compounds resulting from other processes are likewise suitable as insulating oils.

E sample 1 An oil which consists of a mixture of polyethyl naphthalenes boiling at 12 mm pressure from about 160 to 200 C. and having a composition of about 90 percent C and about 10 percent H, has the following properties:

Specific gravity 0.950 Flash point (in an open crucible) 150 C. 15 Pour point below 30 C. Viscosity (at C.) 314 (Engler) Asphalt content 0 Water content 0 Acid number -4 0.05 20 Kissling test (German testing method V Verteerungszahl) 0.07 Dielectric strength 188000 volt/cm The term 188000 volt/cm means that an E. M. F. of 188,000 volt is necessary to cause an electric spark between two electrodes, the distance between the electrodes being 1 cm and the medium between the two electrodes being the insulating oil, the use of which is recommended in the above given example.

E mample 2 An oil which consists of a mixture of polypropyl naphthalenes boiling at 12 mm pressure from about 160 to 200 C. and having a composition of about 90.5 percent C and 9.5 percent H, has the following properties:

reacting with propylene in the presence of aluminium chloride upon ar-chlorotetrahydronaphthalene has a dielectric strength of 165000 volt/cm.

Example 3 An oil which consists of a mixture of ethylated naphthalenes and naphthalenes substituted by higher alkyl groups, prepared by reacting upon naphthalene in the presence of aluminium chloride with waste gas from cracking operations (containing about 23 percent of ethylene and 12 percent of higher homologues thereof), and boiling at 12 mm. pressure from about 160 to 200 C. and having a composition of about 01 percent and 9 percent H, has the following properties:

Specific gravity 0.948 Flash poin 148 C. Pour point below -25 C. Viscosity (at 20" C.) 3.7 (Engler) Asphalt con n 0 Water conten 0 Acid number 0.05

Kisslfipg) test German testing method za Dielectric strength 159000 volt/cm Ewample 4 Verteerungs A mixture which contains equal proportions of a mineral oil (characteristics I) and the oil of Example 3 has the properties given below II C.) s 4.3 4.1 (Englea) Asphalt content 0 I 0 Water content 0 0 Acid number 0.08 0.06

0.07 018 110000 135000 volt/cm 1. An insulating oil comprising a liquid polyalkylated naphthalene compound.

2. An insulating oil comprising a liquid polyalkylated naphthalene hydrocarbon compound having a specific gravity below l.

3. An insulating oil comprising a liquid polyalkylated naphthalene hydrocarbon compound having a specific gravity of from about 0.850 to about 0.950.

4. An insulating oil comprising a liquid polyalkylated naphthalene hydrocarbon compound having saturated side chains with at least two carbon atoms.

5. An insulating oil comprising a polyalkylatednaphthalenehydrocarboncompound having a specific gravity of about 0.950, a viscosity (at 20 C.) below 8 (Engler) a flash po izgt ziove 140 C. and a pour point below 6. A composition of matter comprising an insulating oil containing a substantial prohydrocarbon portion of a polyalkylatednaphthalenehydro- 9. A composition of matter comprising an insulating oil containing a substantial prortion of a polyalkylated naphthalene hgrocarbon compound having saturated si e chains with at least two carbon atoms.

10. A composition of matter com rising a mineral oil containing a substantia proportion of a polyalkylated naphthalene hydrocarbon compound.

11. An insulating oil comprising a liquid naphthalene hydrocarbon compound which is substituted by at least two alkyl groups having at least two carbon atoms.

12. An insulating oil comprising a liquid naphthalene hydrocarbon compound which is substituted by at least two alkyl groups haying 2-3 carbon atoms.

13. An insulating oil comprising a liquid naphthalene hydrocarbon compound having go at least two saturated side chains with 2-3 carbon atoms. a

14; A composition of matter comprising an insulating oil containing a substantial proortion of a liquid naphthalene hydrocaron compound which is substituted by at least't'wo alkyl groups having at least two carbon atoms. 15. A composition of matter comprising an insulating oil containing a substantial pro- 80 portion of a liquid naphthalene hydrocarbon compound WlllCll is substituted by at least two alkyl groups having 2-3 carbon atoms.

16. A composition of matter comprising an insulating oil containing a substantial proportion of a liquid naphthalene hydrocarbon compound having at least two saturated side chains with 2-3 carbon atoms.

. In testimony whereof I have hereunto set 'my hand. 40 RICHARD MICHEL. 

